Overhead cable installation



Patented Nov. 8, 1938 UNITED STATES OVERHEAD CABLE INSTALLATIOlW Frank w. Engster, Washington, D. 0., assignor m General Electric Company, a' corporation of New York Application June 12,

Claims.

The present invention relates to cable installations in which the cables are designed to be supported on poles or other structures in elevated positions. The type'of cable to which my in- 5 vention is directed is of the concentric type and comprises a central insulated conductor operating at high potential surrounding which is a second conductor operating at ground potential so that danger to life is eliminatedin the event of accidental contact with the cable. The inner conductor is made and insulated in the usual way. The outer conductor comprises alternate steel and copper wires or their respective equivalents. The steel wires primarily serve as a mechanical support and armor for the cable and the copper or other wires to carry current at ground potential although some current is or may be carried by the steel wires. In the manufacture of the cable, the steel wires are by external radial pressure caused to form seats in the softer wires and in this manner a self supporting structure is formed in which the wires are interlocked; Because of the construction of the cable, certain problems are present, to wit: Unless precautions are taken in the way of special supports at the poles, the insulation on the inner conductor, due to the weight of the cable, is liable to be injured due to compression pressure by the outer conductor. Such a cable also presents the problem of gaining access to the center conductor for the purpose of making taps for branch lines and of maintaining the continuity of the outer soft wires as a conveyor of current and also of the steel wires as a mechanical support. A further problem is that of preventing longitudinal pull on the center wire, especially when it has to be cut to make a tap or a splice. The problem is enhanced by the fact that the center conductor at times has to be tapped while current at high potential is flowing through it. When a tap has to be made to a live conductor, it is in the language of the industry referred to as a hot tap. Ordinarily house wiring presents no particular problem in this particular but it is quite a different thing where the voltage of the center conductor is measured in thousands, as in the present case.

An object of my invention is the provision of an improved means for securely supporting cable of the character described without injury to the insulation on the inner conductor and at the same time avoiding undue tensile strains in said inner conductor.

A further object of my invention is the provision of improved means whereby the center conductor can readily be tapped and the continuity 1936, Serial No. 84.93%

of the steel supporting wires and of the outer soft metal wires as conductors maintained.

For a consideration of what I believe to be novel and my invention, attention is directed to the accompanying description and the claims appended thereto.

In the drawing, which is illustrative of a construction embodying my invention, Fig. 1 is a view in side'elevation of a cable and its supporting poles; Fig. 2 is a plan view of a pole with the supports for the cable and the tap for the center conductor; Fig. 3 is an enlz rged bottom plan view of a pair of cable supporting clamps and connectors; Fig. 4 is an enlarged view of one form-of support; Fig. 5 is an end view of the same; Fig. 6 is an enlarged sectional view of the cable, and Fig. 7 is a detail view of a splice located between poles.

Referring first to Fig. 6, 1 indicates the center conductor which may be stranded or solid as desired. Around the conductor is a body of insulation t of any suitable material of which a rubber or rubber-like compound may be considered as an example. The outer conductor which operates at ground potential comprises a large number of round wires 9 made of hard drawn steel having high tensile strength. Between or interspersed with the steel wires are other wires Ill initially of rectangular section made of softer metal of which copper or aluminum may be considered as examples. In the manufacture the steel wires are spirally wrapped as in any ordinary cable but without any twist, the purpose being to prevent them from spreading when a transverse cut is made. The soft wires on the other hand are spirally wound and also twisted so that they always stand radially with respect to the axis of the center conductor. Because they are soft, they do not tend to spread when cut. After the hard and soft wires are laid up or spiraled to form the cable, they are passed longitudinaily through a die means which reduces the outside diameter to the proper size and also causes the steel wires to form concave seats in the sides of the soft wires. As a result, the cable is self supporting and the hard and soft wires are interlocked which prevents them from separating.

In Fig. l is shown a cable of the character above described supported on poles ll. Because of the strength of the cable due to the steel wires, the poles may be widely spaced, as for example by 300 feet. The cable shown is intended, but without limitation thereto, to carry current at 2300 volts. The outside diameter is .625. A perconductor and is afterwards covered with insulation. In order to preserve the continuity of the copper or conducting wires I. of the cable, a Jumper 36 made of copper or other good conducting material is provided. Its ends are carefully united with the copper wires ii. For example, a few turns of the wire of which the jumper is composed may be wrapped around the cable and soldered, brazed or welded thereto.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A cable installation comprising elevated supports, suspended main and branch concentric cables, each comprising an insulated central conductor and a surrounding conductor operating at ground potential, the latter comprising supporting wires of high tensile strength and interspersed conducting wires, the said supporting wires of the main cable being cut in the region of a support, clamps secured to the adjacent ends of the cut wires and to the supporting wires of the branch cable, means connecting the clamps of the main and branch cables to the support.in such manner as to prevent a longitudinal pull on the center conductor thereof between the cut ends of the supporting wires, and connectors electrically uniting the center conductor of the main cable and the outer conducting wires thereof with those of the branch cable respectively.

2. A cable installation comprising supports, a main concentric cable having an insulated center conductor and a surrounding bare conductor comprising supporting wires of high tensile strength and conducting wires, both operating at a potential lower than that of the center conductor, the said supporting wires being cut adjacent one of the supports, a clamp applied to the cut ends of the supporting wires of the cable, means connecting the clamps to the support to sustain the weight and pull of the cables located on opposite sides of the support, a branch concentric cable similar in construction to the main cable, a connector electrically uniting the center conductor of the main cable with that of the branch, means for uniting the conducting wires of the main cable with those of the branch, and means for supporting the branch cable.

3. An overhead cable installation comprising elevated supports, suspended main and branch cables, each comprising an insulated center conductor and a surrounding outer bare conductor operating at a potential lower than that of the insulated conductor, said outer conductor comprising a set of supporting wires of high tensile strength and a set of conducting wires, the said supporting wires of the main cable being cut in the region of a support, a clamp secured toeachcableadjacentthecutendsofthesupporting wires and enclosing both sets of wires, means connecting the clamps to the elevated support in such manner as to relieve the portion of thecenter conductor and of the conducting wires located between said out ends of longitudinal pull, means for uniting the conducting wires of the main cable with those of the branch cable, and a' connector for uniting the center conductor of the main cable with that of the branch cable.

4. An overhead cable installation comprising elevated spaced supports, a main cable carried by the supports, said cable terminating adjacent one of the supports and comprising an insulated center conductor and an outer conductor comprising bare wires of high tensile strength and bare conducting wires, said wires being in interlocking arrangement to form a self supporting annulus, a 'tap cable of similar construction, clamping means in which the supporting bare wires of the main cable and of the tap cable are firmly anchored, said insulated conductors extending outwardly through the clamping means,

devices for securing the clamping means of the main and tap cable to a support, said clamping means and devices relieving the insulated conductors of longitudinal strains, a means for electrically connecting the outer conductors of the main and tap cables, and insulated means located at one end of the main cablefor electrically connecting the insulated center conductor thereof to that of the tap cable.

5. An overhead cable installation comprising elevated spaced supports. a main concentric cable carried by the supports and comprising an insulated center conductor and an outer bare conductor surrounding the insulation of the center conductor and comprising bare wires of high tensile strength and bare conducting wires of lesser strength, said wires being interspaced in interlocking arrangement to form a self supporting annulus, a tap cable of similar construction, the ends of the wires of high tensile strength of both main and tap cables being exposed adjacent a selected support, clamps in which the exposed ends of the wires of high tensile strength are firmly secured and through and beyond which the ends of the conducting wires freely extend, a means secured to the selected support and to each of the clamps for sustaining the weight and pull of the connected cables, connector means independent oi the clamping means and located between them in which the ends of the conducting wires are coilectivelysecured, other connector means also located between the clamps for uniting the ends of the insulated center conductors, and insulation for the last named connector means.

MW.ENGBTER.

Nov. 8,1938. K. HEbDmG 2,136,243

ELECTRICAL REGULATING APPARATUS FOR RECTIFIERS Original Filed May 9, 1936 mkzcbe Laad I INVENTOR Lmme KHeddmg HIS ATTORNEY 

